Manufacturing Soft Devices Out of Sheet Materials

ABSTRACT

A soft composite actuator is described, including a first elastomeric layer; a strain limiting layer; and a first radially constraining layer, wherein the first elastomeric layer is disposed between the first radially constraining layer and the strain limiting layer; and the elastomeric layer, the strain limiting layer, and the radially constraining layer are bonded together to form at least one bladder for holding pressurized fluid. Methods of using and making of the soft composite actuator are described.

RELATED APPLICATION

The present application claims priority to U.S. Provisional Application61/885,092, filed Oct. 1, 2013, which is hereby incorporated byreference in its entirety.

INCORPORATION BY REFERENCE

All patents, patent applications and publications cited herein arehereby incorporated by reference in their entirety in order to morefully describe the state of the art as known to those skilled therein asof the date of the invention described herein.

BACKGROUND

Most robots are constructed using so-called “hard” body plans; that is,a rigid (usually metal) skeleton, electrical or hydraulic actuation,electromechanical control, sensing, and feedback. These robots aresuccessful at the tasks for which they were designed (e.g., heavymanufacturing in controlled environments) but have severe limitationswhen faced with more demanding tasks (for example, stable motility indemanding environments): tracks and wheels perform not as efficiently aslegs and hooves.

Evolution has selected a wide range of body plans for mobile organisms.Many approaches to robots that resemble animals with skeletons are beingactively developed: “Big Dog” is an example. A second class ofrobot—those based on animals without skeletons—are much less explored,for a number of reasons: i) there is a supposition that “marine-like”organisms (squid) will not operate without the buoyant support of water;ii) the materials and components necessary to make these systems are notavailable; iii) the major types of actuation used in them (for example,hydrostats) are virtually unused in conventional robotics. These systemsare intrinsically very different in their capabilities and potentialuses than hard-bodied systems. While they will (at least early in theirdevelopment) be slower than hard-bodied systems, they will also be morestable and better able to move through constrained spaces (cracks,rubble), lighter, and less expensive.

Robots, or robotic actuators, which can be described as “soft” are mosteasily classified by the materials used in their manufacture and theirmethods of actuation. Pneumatic soft robotic actuators can bemanufactured using inextensible materials, which rely on architecturessuch as follows. McKibben actuators, also known as pneumatic artificialmuscles (PMAs), rely on the inflation of a bladder constrained within awoven sheath which is inextensible in the axis of actuation. Theresultant deformation leads to radial expansion and axial contraction;the force that can be applied is proportional to the applied pressure.Related actuators are called pleated pneumatic artificial muscles.

There are “soft” robotic actuators such as shape memory alloys whichhave been used both as the actuation method and as the main structuralcomponent in robots which can both crawl and jump. Another approach,which can be described as “soft” uses a combination of traditionalrobotic elements (an electric motor) and soft polymeric linkages basedon Shape Deposition Manufacturing (SDM). This technique is a combinationof 3D printing and milling. An example of a composite of traditionalrobotics with soft elements has been used with success in developingrobotic grippers comprising soft fingers to improve the speed andefficiency of soft fruit packing in New Zealand.

Soft robotics using interconnected channels in a molded elastomeric havebeen reported. Soft robotics can be actuated using pneumatic pressure tocause the robot to undergo a range of motions. The basic soft roboticactuator includes an extensible channel or bladder that expands againsta stiffer or less extensible backing. See, PCT Appln. Ser. No.PCT/US11/61720 for additional information on the design and actuation ofsoft robotics, the contents of which are incorporated in its entirety byreference.

Molding is one way to make soft robotic actuators; however, it is abatch process. There thus remains a need for low cost, simple, and highthroughput methods for making soft robotics. There also remains a needfor new, simple, and efficient designs for soft robotic actuationdevices.

SUMMARY

Described herein are soft composite actuators which can be producedeasily and efficiently. The soft composite actuator as disclosed hereincan be manufactured by bonding two or more material layers or sheetstogether. The material layers may be bonded together to form one or morebladder configured to hold pressurized fluid. The soft compositeactuator may be actuated when the bladder therein is pressurized byinfusing fluids into the bladder. The bonding may be achieved bymechanical, thermal, and/or chemical means or combination thereof. Thesoft composite actuator as disclosed herein can be manufactured withoutusing any mold.

In some embodiments, one of the material layers is made of athermoplastic elastomer material which can be thermally bonded (or highfrequency welded or ultrasonically welded) together with other layers todefine the actuator's bladder (e.g., air tight bladders). Theseconstructions could also be achieved with chemical and mechanical bondsor a combination thereof. Methods of making and using the soft compositeactuator are also disclosed herein.

In one aspect, a soft composite actuator is described, including:

-   -   a strain limiting layer;    -   a first radially constraining layer; and    -   a first elastomeric layer disposed between the first radially        constraining layer and the strain limiting layer;        wherein    -   the first elastomeric layer, the strain limiting layer, and the        first radially constraining layer are bonded together to form at        least one bladder for holding pressurized fluid.

In any embodiment described herein, the bond is selected from the groupof thermal bonds, chemical bonds, mechanical bonds and combinationsthereof.

In any embodiment described herein, the soft composite actuator furtherincludes a second elastomeric layer disposed adjacent to the firstelastomeric layer and the strain limiting layer comprises a secondradially constraining layer.

In any embodiment described herein, the radially constraining layerincludes one or more radially constraining sections.

In any embodiment described herein, the radially constraining sectionsincludes radially constraining strips evenly or unevenly distributed inthe radially constraining layer.

In any embodiment described herein, the radially constraining strips areoriented parallel to one of the edges of the radially constraining layeror at an angle to one of the edges of the radially constraining layer.

In any embodiment described herein, the radially constraining strips arebonded to the first elastomeric layer.

In any embodiment described herein, the radially constraining layerincludes one or more strain limiting sections free from any openings.

In any embodiment described herein, the radially constraining layerincludes:

-   -   one or more openings through which one or more portions of the        adjacent first elastomeric layer expand upon actuation, and    -   one or more strain limiting sections free from any openings.

In any embodiment described herein, the first elastomeric layer, thestrain limiting layer, and the first radially constraining layer arebonded together to form a plurality of bladders for holding pressurizedfluid.

In any embodiment described herein, the soft composite actuator furtherincludes one or more rigid elements attached to the strain limitinglayer.

In any embodiment described herein, the bladder is designed toaccommodate a pressurized fluid selected from the group consisting of agas and a liquid.

In any embodiment described herein, one of the elastomeric layer, thestrain limiting layer, and the radially constraining layer is configuredto absorb fluids, transmit light, change color or luminescence, embed asoft sensor or a medical patch, embed at least a part of an electroniccircuit or a heating element, and a combination thereof.

In any embodiment described herein, the soft composite actuator is partof a splint, a grasper, or a glove comprising a plurality of digits, oris a splint, a grasper, or a glove.

In another aspect, a soft composite actuator is described, including:

-   -   a monolithic, first composite layer including one or more first        elastomeric sections and one or more first radially constraining        sections; and    -   a strain limiting layer,        wherein    -   the first composite layer and the strain limiting layer are        bonded together to form at least one bladder for holding        pressurized fluid.

In any embodiment described herein, the strain limiting layer includes amonolithic, second composite layer including one or more secondelastomeric sections and one or more second radially constrainingsections.

In any embodiment described herein, the first and/or second elastomericsection, the first and/or second radially constraining section, and thefirst and/or second composite layer have the same thickness.

In any embodiment described herein, the first and/or second elastomericsection and the first and/or second radially constraining section havedifferent thickness.

In any embodiment described herein, the first and/or second radiallyconstraining section is encapsulated in the first and/or secondelastomeric section.

In any embodiment described herein, the first and/or second elastomericsections and the first and/or second radially constraining sections arebonded together.

In any embodiment described herein, the bond is selected from the groupof thermal bonds, chemical bonds, mechanical bonds and combinationsthereof.

In any embodiment described herein, the radially constraining sectionscomprise radially constraining strips oriented parallel to one of theedges of the composite layer or at an angle to one of the edges of thecomposite layer.

In any embodiment described herein, the radially constraining strips areevenly or unevenly distributed in the composite layer.

In any embodiment described herein, the first composite layer and thestrain limiting layer are bonded together to form a plurality ofbladders for holding pressurized fluid.

In any embodiment described herein, the soft composite actuator furtherincludes one or more rigid elements attached to the strain limitinglayer.

In any embodiment described herein, the bladder is designed toaccommodate a pressurized fluid selected from the group consisting of agas and a liquid.

In any embodiment described herein, one of the layers is configured toabsorb fluids, transmit light, change color or luminescence, embed asoft sensor or a medical patch, embed at least a part of an electroniccircuit or a heating element, and a combination thereof.

In any embodiment described herein, the soft composite actuator is partof a splint, a grasper, or a glove comprising a plurality of digits, oris a splint, a grasper, or a glove.

In yet another aspect, a soft actuating device including a plurality ofthe soft composite actuators of any one of embodiments is described.

In any embodiment described herein, the soft actuating device includes:

-   -   a first soft composite actuator connected to a first fluid        source; and    -   a second soft composite actuator connected to a second fluid        source.

In yet another aspect, a method of actuation is described, including:

-   -   providing a soft composite actuator of any one of embodiments;        and    -   pressurizing the bladder with a fluid, wherein the soft        composite actuator actuates in a predetermined manner.

In any embodiment described herein, actuation of the soft compositeactuator achieves one or more motions selected from the group consistingof bending motion, combination bending, twisting motion, linearextension, a combination of linear extension and twist, linearcontraction, a combination of linear contraction and twist, and anycombination thereof.

In any embodiment described herein, the soft composite actuator isconfigured to open an incision or move, displace organs, muscle, and/orbone, brace a joint, be worn to support joint movements, shape-match anobject, fold pre-defined bending joints to create origami-likestructures, achieve a sufficient grasp over the object, or create apadded layer conformal to the object.

In any embodiment described herein, the pressurized fluid istemperature-regulated.

In any embodiment described herein, the soft composite actuator stiffensupon fluid pressurization.

In any embodiment described herein, the bladder is configured to beinflated to a first degree of stiffness under a first fluid pressure orto a second degree of stiffness under a second fluid pressure differentfrom the first fluid pressure.

In any embodiment described herein, the actuator is actuated todistribute forces, mixing material, handling material, lifting,grasping, steering a photovoltaic cell or a mirror, steering material ona surface.

In yet another aspect, a method of actuation is described, including:

-   -   providing the soft actuating device of any one of the        embodiments described herein; and    -   pressurizing one or more bladders with one or more fluids,        wherein the soft actuating device actuates in a predetermined        manner.

In yet another aspect, a method of actuation is described, including:

-   -   providing the soft actuating device of any one of the        embodiments described herein; and    -   pressurizing the first soft composite actuator's bladder and the        second soft composite actuator's bladder alternately by        activating the first fluid source and the second fluid source        alternately.        the first soft composite actuator bends upon actuation and the        second soft composite actuator stiffens upon actuation.

In yet another aspect, a method of making a soft composite actuator ofany one of the embodiments described herein is disclosed, including:

-   -   providing a first elastomeric layer, a strain limiting layer,        and a first radially constraining layer; wherein the elastomeric        layer is disposed between the radially constraining layer and        the strain limiting layer; and    -   bonding the first elastomeric layer, the strain limiting layer,        and the first radially constraining layer to form sealed        parameters defining at least one bladder for holding pressurized        fluid.

In any embodiment described herein, providing a first elastomeric layer,a strain limiting layer, and a first radially constraining layerincludes:

-   -   providing a pre-stacked laminate comprising a first elastomeric        laminate layer, a strain limiting laminate layer, and a first        radially constraining laminate layer; and    -   separating part of the laminate to provide the first elastomeric        layer, the strain limiting layer, and the first radially        constraining layer stacked together.

In yet another aspect, a method of making a soft composite actuator ofany one of the embodiments described herein is disclosed, including:

-   -   providing the first composite layer and the strain limiting        layer; and    -   bonding the first composite layer and the strain limiting layer        to form sealed parameters defining at least one bladder for        holding pressurized fluid.

In any embodiment described herein, providing the first composite layerand the strain limiting layer including:

-   -   providing a pre-stacked laminate comprising a first composite        laminate layer and a strain limiting laminate layer; and    -   separating part of the laminate to provide the first composite        layer and the strain limiting layer stacked together.

In any embodiment described herein, the bond is selected from the groupof thermal bonds, chemical bonds, mechanical bonds and combinationsthereof.

In any embodiment described herein, the elastomeric layer, the strainlimiting layer, and the radially constraining layer are contained in apackage.

In any embodiment described herein, bonding is achieved by external heatpassing through the packaging or internal heat generated by a heatingelement inside the packaging without the compromise of the package.

In any embodiment described herein, the elastomeric layer or the firstcomposite layer is in a pre-strained state before bonding.

In any embodiment described herein, one of the layers has a non-planarshape before or during bonding.

The combination of any one embodiment described herein with any otherone or more embodiments described herein is contemplated.

Unless otherwise defined, used or characterized herein, terms that areused herein (including technical and scientific terms) are to beinterpreted as having a meaning that is consistent with their acceptedmeaning in the context of the relevant art and are not to be interpretedin an idealized or overly formal sense unless expressly so definedherein. For example, if a particular composition is referenced, thecomposition may be substantially, though not perfectly pure, aspractical and imperfect realities may apply; e.g., the potentialpresence of at least trace impurities (e.g., at less than 1 or 2%) canbe understood as being within the scope of the description; likewise, ifa particular shape is referenced, the shape is intended to includeimperfect variations from ideal shapes, e.g., due to manufacturingtolerances. Percentages or concentrations expressed herein can representeither by weight or by volume.

Although the terms, first, second, third, etc., may be used herein todescribe various elements, these elements are not to be limited by theseterms. These terms are simply used to distinguish one element fromanother. Thus, a first element, discussed below, could be termed asecond element without departing from the teachings of the exemplaryembodiments. Spatially relative terms, such as “above,” “below,” “left,”“right,” “in front,” “behind,” and the like, may be used herein for easeof description to describe the relationship of one element to anotherelement, as illustrated in the figures. It will be understood that thespatially relative terms, as well as the illustrated configurations, areintended to encompass different orientations of the apparatus in use oroperation in addition to the orientations described herein and depictedin the figures. For example, if the apparatus in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the exemplary term, “above,” may encompass both an orientation ofabove and below. The apparatus may be otherwise oriented (e.g., rotated90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Further still, in thisdisclosure, when an element is referred to as being “on,” “connectedto,” “coupled to,” “in contact with,” etc., another element, it may bedirectly on, connected to, coupled to, or in contact with the otherelement or intervening elements may be present unless otherwisespecified.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of exemplary embodiments.As used herein, singular forms, such as “a” and “an,” are intended toinclude the plural forms as well, unless the context indicatesotherwise. Additionally, the terms, “includes,” “including,” “comprises”and “comprising,” specify the presence of the stated elements or stepsbut do not preclude the presence or addition of one or more otherelements or steps. The term “laminate” and “soft composite actuator” maybe used interchangeably.

DESCRIPTION OF THE DRAWINGS

The invention is described with reference to the following figures,which are presented for the purpose of illustration only and are notintended to be limiting. In the Drawings:

FIG. 1A presents an exploded and assembled view of an actuatable devicecapable of bending that includes two layers bonded together such thatthe bond defines an airtight (or water tight) bladder: one layer havingstrain limiting properties and the other layer having elasticproperties, according to one or more embodiments described herein.

FIG. 1B presents a perspective view of the two-layer bending actuatorunder fluid pressurization where the elastic layer swells and grows inradius and in length, according to one or more embodiments describedherein.

FIG. 1C is a perspective view of the two-layer bending actuator underfluid pressurization where at a certain pressure the swelling elasticlayer will cause the strain limited layer to bend, according to one ormore embodiments described herein.

FIG. 2A is an exploded and assembled view of an actuatable devicecapable of bending that includes three layers bonded together such thatthe bond defines an airtight (or water tight) bladder, including: onelayer having radial strain limited properties, one layer having elasticproperties, and another layer having strain limiting properties,according to one or more embodiments described herein.

FIG. 2B is a side view of the three-layer bending actuator according toone or more embodiments described herein under fluid pressurizationwhere the radially constraining layer limits radial expansion of theelastic layer and promotes linear growth by allowing the elastic layerto expand via the cut outs of the radially constraining layer.

FIGS. 2C-G describe a process where two radially constraining layers andtwo elastic layers can be bonded to form a linear extending actuator,according to one or more embodiments described herein.

FIG. 2C presents an exploded view of the layer assembly, according toone or more embodiments described herein.

FIG. 2D depicts half of the assembly where after bonding, the excessmaterial from the radially constraining layer can be removed leavingstrain limiting strips bonded to the elastic layer, according to one ormore embodiments described herein.

FIG. 2E is a cross-section view of the laminate without and with fluidpressurization, according to one or more embodiments described herein.

FIG. 2F is a perspective view of the linear extending actuator in anunpressurized state, according to one or more embodiments describedherein.

FIG. 2G is a perspective view of the linear actuator according to one ormore embodiments described herein extending under fluid pressurizationwhere the strain limiting strips, connected by the bond, form radiallyconstraining hoops along the length of the actuator, thus promotinglinear extension.

FIG. 2H demonstrates that changing the orientation of the strainlimiting strips to the longest dimension of the actuator can be used asan approach to make a contracting linear actuator (i.e., the largestdeformation is contractile), according to one or more embodimentsdescribed herein.

FIG. 3A presents an exploded view of a bending actuatable deviceincluding layers preformed to a particular shape before or duringassembly so that the actuator takes on a non-planar profile in itsunpressurized state, according to one or more embodiments describedherein.

FIG. 3B presents a perspective view of the assembled bending actuator inits unpressurized state, according to one or more embodiments describedherein.

FIG. 3C presents a side view of the bending actuator in a pressurizedstate, according to one or more embodiments described herein.

FIG. 4A presents an exploded and assembled view of a bending actuatabledevice including two layers, where one layer has anisotropic propertiessuch that it prefers to stretch along the y-axis and is strain-limitedalong the x-axis and the other layer is strain limited in both the x andy direction, according to one or more embodiments described herein.

FIG. 4B presents a side view of the two-layer bending actuator underfluid pressurization, wherein the anisotropic layer performs a dualfunction of promoting linear growth while limiting radial expansion tocause the assembly to bend, according to one or more embodimentsdescribed herein.

FIG. 4C is a perspective view of an assembled linear-extending actuatorincluding two anisotropic layers bonded together to form an airtight (orwater tight) bladder, according to one or more embodiments describedherein.

FIG. 4D is a side view of the linear-extending actuator under fluidpressurization where the strain limiting portions of the anisotropiclayer form hoops that limit radial expansion and promote linearextension, according to one or more embodiments described herein.

FIG. 4E is an exploded and assembled view of an actuatable devicecapable of bending and twisting under fluid pressurization, according toone or more embodiments described herein.

FIG. 4F is an exploded and assembled view of an actuatable devicecapable of linear extension and twisting under fluid pressurization bybonding two anisotropic layers with angled elastic and strain limitingelements, according to one or more embodiments described herein.

FIG. 5A shows the profile of a radially constraining layer (top) and theresponse of the actuator (bottom) under fluid pressurization, accordingto one or more embodiments described herein.

FIG. 5B is an extension of FIG. 5A demonstrating that several joints canbe designed into a single actuator to form a closed shape, according toone or more embodiments described herein.

FIG. 5C is an extension of FIG. 5A, demonstrating that multiple bendingactuators can be combined on a single laminate, according to one or moreembodiments described herein.

FIG. 6A depicts a top view and an isometric view of an actuatable devicethat combines a multiple functions onto a single laminate, where twobending actuators are connected via two stiffeners, according to one ormore embodiments described herein.

FIG. 6B is an extension of FIG. 6A where multiple stiffeners can be usedto support bending actuators and achieve greater coverage, according toone or more embodiments described herein.

FIG. 7A depicts an exploded view and cross-section view of an actuatabledevice that incorporates rigid elements as an additional layer that canbe used to define bending points, adjust the bending radius ofcurvature, improve force transmission, and act as a mounting substratefor auxiliary equipment, according to one or more embodiments describedherein.

FIG. 7B is a side view of a bending actuator under fluid pressurizationwith rigid elements where it only bends at the gaps between the rigidelements, according to one or more embodiments described herein.

FIG. 8A is an exploded view of a bimorph bending actuator that consistsof a single bending actuator and incorporates a pre-strained layerduring the assembly, according to one or more embodiments describedherein.

FIG. 8B shows the range of motion of the bimorph bending actuator atdifferent stages of pressurization, according to one or more embodimentsdescribed herein.

FIG. 8C illustrates that opposing bimorph bending actuators can be usedto form a grasper, according to one or more embodiments describedherein.

FIG. 9A is an extension of FIG. 4C where multiple linear extendingactuators can be grouped on the same laminate to form a multi-degree offreedom bending and extending actuator, according to one or moreembodiments described herein.

FIG. 9B is an end view of FIG. 9A and depicts the next stage in thefabrication of a multi-degree of freedom bending and extending actuatorwhere the laminate is bonded end to end to form a tube shape, accordingto one or more embodiments described herein.

FIG. 9C illustrates that when one bladder is pressurized it willlinearly extend causing the tube structure to bend, according to one ormore embodiments described herein.

FIG. 10 is a perspective view of a wearable application where softactuators have been incorporated into a glove to assist joint motions,according to one or more embodiments described herein.

FIG. 11 is perspective view of a material layer demonstratingmulti-functionality and optionally incorporating electronics, heatingelements, sensors, and so forth, according to one or more embodimentsdescribed herein.

FIG. 12 shows a sequence of side views of an actuatable device that usesconnected pressurized bladders to transmit force, according to one ormore embodiments described herein.

FIG. 13A shows a sequence of images where a rolled sheet of actuatabledevices can be cut to a desired length and the bladders can be resealedwith a sealing tool, according to one or more embodiments describedherein.

FIG. 13B illustrates how these sheets of actuatable devices can besealed and bonded together to form a range of different actuatablestructures, according to one or more embodiments described herein.

FIG. 14 depicts a process by which the bladders of actuatable devicescan be defined while the layers of the laminate are contained withinpackaging (both sterile and non-sterile), according to one or moreembodiments described herein.

DETAILED DESCRIPTION

Described herein are soft composite actuators made by bonding two ormore material layers. A material layer, as used herein, may refer to anelastomeric layer, a strain limiting layer, a radially constraininglayer, or a first or second composite layer including one or moreelastomeric sections and one or more radially constraining sections. Theelastomeric layer, as used herein, refers to a layer which is made ofone or more elastic materials and can be bent, curved, twisted, orsubjected to any other motion to change its shape and/or orientationunder pressure. Non-limiting examples of the elastic material includeelastic polymer (e.g. urethanes and silicones), thermoplastic elastomers(TPEs), thermoplastic urethanes (TPUs) and so forth. As used herein,“elastomeric” and “elastic” are used interchangeably.

In some embodiments, the material layer is a strain limiting layer. Thestrain limiting layer, as used herein, refers to any layer which is notelastic or less elastic than the elastomeric layer. As a result, underactuation (e.g., pressurization of the bladder), the changes in theshape or orientation of the elastomeric layer, not that of the strainlimiting layer, will predominantly determine the shape, curvature,and/or orientation of the soft composite actuator after actuation. Insome embodiments, the strain limiting layer is made of one or morestrain limiting materials. Non-limiting examples of the strain limitingmaterial include fibers, thread, non-woven materials, and higherduromoter materials to name a few. Any other materials known in the artsuitable as the strain limiting material can be used.

In other embodiments, the material layer is a radially constraininglayer which limits the radial expansion of the resulting bladder andpromotes efficient bending. In some specific embodiments, the radiallyconstraining layer can have strain limiting properties such as those ofthe strain limiting layer. The radially constraining layer employs thestrain limiting material to restrict the radial expansion of the bladderin the soft composite actuator. In one or more embodiments, the radiallyconstraining layer is a sheet of high durometer material that containsopenings, e.g., cutouts, which provide radially constraining regions(e.g., strips or bands) of spaced at locations to allow portions of theadjacent elastomeric layer to expand through the cutouts. The radiallyconstraining regions are positioned and arranged (e.g., as bands orstripes traversing the width of the soft composite actuators) so thatthe elastomeric layer's radial expansion will be limited or restricted.In some embodiments, the radially constraining regions are evenly orunevenly distributed in the radially constraining layer. In somespecific embodiments, the radially constraining regions, e.g., strips220 in FIG. 2C, are oriented parallel to one of the edges of theradially constraining layer or at an angle to one of the edges of theradially constraining layer. The angle (θ) can be in any ranges or haveany values. In some embodiments, θ is about 10, 20, 30, 40, 45, 50, 60,70, 80 degree, or in any ranges bound by any two of the values disclosedherein.

In some specific embodiments, the radially constraining layer or sectionrestrict the radial swelling of the bladder or elastomeric layer topromote more efficient bending of the actuator by supporting linearextension of the elastic layer and limiting radial expansion, which doesnot promote bending. In still other embodiments, the radiallyconstraining region can be incorporated into a layer containing othermaterials. By way of example, the radially constraining layer or strainlimiting layer can be a monolithic composite layer, e.g., layer 401 inFIG. 4A, comprising one or more elastomeric sections and one or moreradially constraining sections. The elastomeric section may be made ofelastomeric materials and the radially constraining section may be madeof strain limiting materials.

In certain embodiments, the radially constraining layer comprises one ormore individual radially constraining sections, which can be assembledand bonded to form a radially constraining layer. In certain specificembodiments, the radially constraining sections comprise radiallyconstraining strips evenly or unevenly distributed in the radiallyconstraining layer. The radially constraining strips, e.g., strips 405in FIG. 4A, may be oriented parallel to one of the edges of the radiallyconstraining layer or at an angle to one of the edges of the radiallyconstraining layer. The angle (θ) can be in any ranges or have anyvalues. In some embodiments, θ is about 10, 20, 30, 40, 45, 50, 60, 70,80 degree, or in any ranges bound by any two of the values disclosedherein. The radially constraining strips may be bonded to the firstelastomeric layer.

In some embodiments, the material layer is a radially constraining layerdescribed above.

The two or more material layers are bonded together to form sealed atleast one bladder for holding pressurized fluid. In some embodiments,the perimeters or certain portions of two adjacent material layers inthe soft composite actuator are bonded together to result in afluid-tight bladder, except that the bladder may be connected to a fluidinfusion/vacuum source. In certain embodiments, the perimeters orcertain portions of the adjacent elastomeric layer and the strainlimiting layer in the soft composite actuator are bonded together toresult in a fluid-tight bladder. In other embodiments, the perimeters orcertain portions of the adjacent first composite layer and the strainlimiting layer in the soft composite actuator are bonded together toresult in a fluid-tight bladder. In still other embodiments, theperimeters or certain portions of the adjacent first composite layer andthe second composite layer in the soft composite actuator are bondedtogether to result in a fluid-tight bladder. In still other embodiments,the soft composite actuator comprises two elastomeric layers and theperimeters or certain portions of the two adjacent elastomeric layersare bonded together to result in a fluid-tight bladder.

In other embodiments, the radially constraining layer comprises one ormore strain limiting sections free from any openings. Thus, the radiallyconstraining layer may include one or more openings through which one ormore portions of the adjacent first elastomeric layer expand uponactuation, and one or more strain limiting sections free from anyopenings. Upon actuation, such soft composite actuator may bend at theportion of the radially constraining layer having the openings and maystiffen at the portion of the radially constraining layer free from anyopenings.

In some embodiments, the bladder is airtight except its connection to anexternal fluid source to infuse pressurized fluid into the bladder.Non-limiting examples of the fluids include a gas and a liquid.Non-limiting examples of the fluid source include a gas tank, a gascylinder, a liquid pump, compressor, gases given off by a chemicalreaction, and so forth. The gas may be air, nitrogen, or one of theinert gases. The liquid may include water, aqueous solution, and organicsolvents or solutions. Upon actuation (e.g., when the bladder is infusedwith pressurized fluid), the soft composite actuator may actuate in apre-determined way to change the actuator's shape, size, orientation,and/or curvature, to achieve one or more desirable functions. The softactuator may have one bladder or a plurality of bladders connected tothe same or different fluid sources.

In one aspect, a soft composite actuator is described, includingcomprising:

-   -   an elastomeric layer;    -   a strain limiting layer; and    -   a radially constraining layer,        wherein    -   the elastomeric layer is disposed between the radially        constraining layer and the strain limiting layer; and    -   the elastomeric layer, the strain limiting layer, and the        radially constraining layer are bonded together to form at least        one bladder for holding pressurized fluid.

The strain limiting layer may be located at the top or bottom of thesoft composite actuator. The layered soft composite actuator allows forthe control of the direction of expansion. For instance, FIGS. 1-3 showthat the soft composite actuator can be constructed by layeringmaterials of different elasticity and subtracting material (e.g.,elastomeric layer, strain limiting layer, and radially constraininglayer).

The actuation mechanism of the soft composite actuator is firstdescribed with reference to FIGS. 1A-1C. As shown in FIG. 1A, an elasticlayer 101 and a strain limiting layer 103 are bonded at the layers'perimeter 105. The bonding may be achieved thermally, mechanically,and/or chemically. In some embodiments, the elastic layer is made ofelastic polymers which can be thermally bonded to other layers such asthe strain limiting layer. The term “elastic layer” or “elastic section”(described below), as used herein, refers to any material layer orsection made of material having elastic properties and can bend orexpand under pressure. The term “strain limiting layer”, as used herein,refers to any material layer which is not elastic or less elastic thanthe elastic material forming the elastic layer or the elastic section inthe composite layer described below. The bonding of the elastic layer101 and the strain limiting layer 103 results in the formation of anairtight bladder 107, which is sealed off except its connections to anoutside fluid infusion/vacuum source configured to inflate or deflatethe bladder by infusing and removing the fluid in and out of thebladder.

Thus, when two different material layers (i.e., one elastic layer 101and one strain limiting layer 103) are bonded to form a bladder, theresulting structure 109 has an anisotropic response to pressurized fluidin the bladder. The elastic layer 101 expands while the strain limitinglayer 103 undergoes limited expansion. The difference in strainresponses between the two layers may cause the structure to bend in thedirection of the strain limited layer (FIG. 1C). FIG. 1B illustrates thesoft composite actuator with a bladder 111 partially filled by pressuredfluid from the fluid infusion/vacuum source 115. The partially filledbladder has an inside pressure higher than the outside pressure (Op) sothat the elastic layer 113 is curved. When the bladder is fully filledby the pressured fluid, the linear growth of the portion of the elasticlayer forming the inflated air tight bladder (portion 117 in FIG. 1C)will eventually cause the strain limited layer 119 to bend. Thecircumferential constraint, i.e., the bonding at the perimeter 105, isbeneficial because without such circumferential constraints, thematerial layer has considerable radial growth which after a certainpoint (e.g., when the material approaches its yield stress or fatigueyield stress), is not useful for the purposes of the bending.

A soft composite actuator according to one or more embodiments isdescribed with reference to FIGS. 2A-2H. As shown in FIG. 2A, anelastomeric layer 203 is disposed between a radial constraining layer201 and a strain limiting layer 205. The perimeters of layers 201, 203,and 205, e.g., portion 207 are bonded together thermally to result insoft composite actuator 209, which upon actuation bends in apredetermined fashion (FIG. 2B). The bonding may also be achieved bychemical method, mechanical method, and a combination thereof. One ofthe advantages of the instant application is that the soft compositeactuator described herein can be made without using any mold, thus themanufacture process is greatly simplified. In some embodiments, heat canbe applied to two or more material layers, e.g., elastomeric layer andstrain limiting layer, to bond the layers together. In otherembodiments, mechanical force by hand or machine can be applied to twoor more material layers, e.g., elastomeric layer and strain limitinglayer, to bond the layers together. In still other embodiments, chemicalreactants can be deposited between the material layers or embedded inone or more material layers and a chemical reaction may be initiated tobond the two or more material layers, e.g., elastomeric layer and strainlimiting layer, together.

As shown in FIG. 2B, the soft composite actuator 209 contains a bladderformed by the bonding of the perimeters of layers 201 and 203. Thisbladder (213 in FIG. 2B) is connected to an infusion/vacuum source 211to infuse pressurized liquid into bladder 213. The fluid-filled bladderhas an inside pressure higher than the outside pressure (Op) whichforces the elastomeric layer 203 and the radially constraining layer 201to bend towards the strain limiting layer 205.

Thus, as shown in FIGS. 2A-2C, an additional layer, i.e., the radiallyconstraining layer, can be added to create an additional anisotropicresponse by limiting the radial expansion of the elastic layer. Thecutouts (215) on the radially constraining layer allow the elastic layerto expand lengthwise while limiting strain limiting regions or bands 216limit radial expansion. Restricting the radial swelling of the bladderpromotes more efficient bending by supporting linear extension of theelastic layer and limiting radial expansion, which does not promotebending. It should be noted that additional layers could be added toinclude other functionalities such as super absorbent material to soakup fluids, antibacterial properties, hot therapy, and cold therapy.

The soft composite actuator can be designed and configured to actuate ina predetermined manner upon pressurization of the bladder and/or performone or more desirable functions. Upon actuation, the soft compositeactuator may be designed to generate structural anisotropy or structuralisotropy. That is, the soft composite actuator may upon actuationgenerate the same or different structural changes when measured alongdifferent axes of the soft composite actuator.

In some embodiments, the soft composite actuator further includes asecond elastomeric layer, and a bladder can be formed by, for example,thermally sealing the edges of the two elastomeric layers. In someembodiments, the strain limiting layer in the soft composite actuator isalso a radially constraining layer which limits the radial expansion ofthe elastomeric layer. These designs are described with reference toFIGS. 2C-2G, which show a linear extending actuator including tworadially constraining layers and two elastic layers bonded to form alinear extending actuator.

As shown in FIG. 2C, a first and second elastomeric layers, 223 and 225,respectively, are sandwiched between a first radially constraining layer217 and a strain limiting layer (i.e., a second radially constraininglayer 221). The radially constraining layers 217 and 221 contain cutouts219 and 227, respectively. After layers 217, 223, 225, and 221 arebonded at their perimeters, e.g., edge 229, to form composite 231, someportions of the soft composite actuator, e.g., portions 235 and 237, canbe cut off along the dotted lines shown in FIG. 2D to form softcomposite actuator 233. These excess materials from the radiallyconstraining layers 217 and 221 are removed leaving strain limitingstrips 243 bonded to the elastic layers. FIG. 2E is a cross-section viewof the soft composite actuator 233 without (upper portion of FIG. 2E)and with fluid pressurization (lower portion of FIG. 2E). As shown inFIG. 2E, the soft composite actuator has layers 217, 221, 223, and 225bonded together at the edge 229. Upon actuation, bladder 239 betweenlayers 223 and 225 is pressurized to generate an inside pressure of P₁,which is greater than the outside pressure P_(atm). As a result, thelayers of the actuator 233 curve as shown in the lower portion of FIG.2E.

FIG. 2F is a perspective view of the linear extending actuator 233 in anunpressurized state. Edges of the layers, e.g., 241 and 247, are bonded(FIG. 2G). FIG. 2G is a perspective view of the linear actuator 233 inthe actuated state extending under fluid pressurization where the strainlimiting strips 243 in the radially constraining layer 217, connected bythe bond at edge 241, form radially constraining hoops along the lengthof the actuator, and thus promote linear extension along the directionof axis 245.

FIG. 2H demonstrates that when the orientation of the strain limitingstrips 251 run length wise, i.e., along axis 253, the resulting softcomposite actuator is a contracting linear actuator 249, (i.e. thelargest deformation is contractile). FIG. 2H shows the contractinglinear actuator 249 in its unactuated state (upper left corner of FIG.2H) and actuated state (lower right corner of FIG. 2H).

In certain embodiments, the pressurized fluid is temperature-regulatedto deliver hot or cold therapy. For instance, fluidic lines could alsobe heat stamped into a material layer for delivery hot and/or coldtherapy or even medicine.

As shown in FIGS. 2A-2H, the elastomeric layer, the strain limitinglayer, and the radially constraining layer may have a planar shapebefore or during bonding. In some other embodiments, at least of theelastomeric layer, the strain limiting layer, and the radiallyconstraining layer may have a non-planar shape before or during bonding.

In one or more embodiments, one or more layers of the soft compositeactuator can be preformed into a non-planar shape before assembly. FIG.3A is an exploded view of a bending soft composite actuator includinglayers that are preformed to a particular shape before or duringassembly so that the actuator takes on a non-planar profile in itsunpressurized state. The soft composite actuator includes the pre-formedradially constraining layer 301, a pre-formed elastic layer 303, and astrain limiting layer 305. These material layers are bonded at theperimeters of the material layers, e.g., perimeter 307 to form a bendingsoft composite actuator 309 (FIG. 3B). The bladder formed in theactuator 309 is connected to a pressurized fluid source via a tube 311.Other types of connection known in the art are contemplated. FIG. 3B isa perspective view of the assembled bending actuator 309 in itsunpressurized state. FIG. 3C is a side view of the bending actuator in apressurized state. When the actuator 309 is actuated by infusion ofpressurized fluid through tube connection 311, radially constraininglayer 301 restricts the radial expansion of the elastic layer 303 andactuator 309 bends in a predetermined matter, i.e., towards thedirection of strain limiting layer 305.

Thus, in some embodiments, it may be advantageous to pre-form (e.g.,thermally form) one or more material layers, e.g., radially constraininglayer, first and second composite layers (also referred to anisotropiclayer in FIGS. 4A-F), elastic layer, or strain limiting layer, before orduring actuator assembly so that an actuator can be designed to achievea particular thickness (or pressurized profile) under fluidpressurization. In some embodiments, preforming one or more materials isdesirable for a soft composite actuator to achieve desired range ofmotion, stiffness, and force production as these outputs are linked toactuator thickness. Pre-forming to a non-planar initial state may alsoplace less strain on the material to reach a target state, which inturn, may reduce the required input pressure and material fatigue.Non-limiting examples of the non-planar shapes of the material layersinclude half cylinder shape (FIGS. 3A-3C), rectangular, tapered, andbellows-shaped. Any material layer of any of the soft composite actuatormay be pre-formed.

In another aspect, a soft composite actuator is described, including:

-   -   a monolithic, first composite layer comprising one or more first        elastomeric sections and one or more first radially constraining        sections; and    -   a strain limiting layer,        wherein    -   the first composite layer and the strain limiting layer are        bonded together to form at least one bladder for holding        pressurized fluid.

The first composite layer is located at the top or bottom of the softcomposite actuator. In some embodiments, the first elastomeric section,the first radially constraining section, and/or the first compositelayer have the same thickness. In these embodiments, the first compositelayer can be made by from bonding the first elastomeric sections and thefirst radially constraining sections together. In other embodiments, thefirst elastomeric section and the first radially constraining sectionhave different thickness. In these embodiments, the first compositelayer and the first elastomeric section may have the same thickness. Insome specific embodiments, the first elastomeric section is thicker thanthe first elastomeric section and/or the first elastomeric sectionencapsulates the first radially constraining section.

The soft composite actuator according to this aspect is described withreference to FIGS. 4A-4F. FIG. 4A is an exploded and assembled view of asoft composite actuator 403 capable of bending and including a firstcomposite layer 401. The first composite layer 401 has radiallyconstraining sections 405 made of strain limiting materials andelastomeric section 407 made of elastic materials. Sections 405 and 407can be in any shape or size and are bonded together by thermal,chemical, and/or mechanical methods to form the monolithic firstcomposite layer 401. Because the first composite layer 401 has differentexpansion properties or characteristics along the x and y axes (i.e.,layer 401 may expand more easily along the y axis than alone the xaxis), the first composite layer 401 is also referred to as a monolithicanisotropic layer. As shown in FIG. 4A, sections 405 and 407 both havethe same thickness as that of the monolithic layer. The first compositelayer is then bonded with a strain limiting layer 409 to form thebending soft composite actuator 403.

Thus, in the embodiments described in FIG. 4A, the first composite layer401 has anisotropic properties such that it prefers to stretch along they-axis and is strain-limited along the x-axis. The strain limiting layer409 is made of strain limiting material and strain-limited is both the xand y directions. The layers are bonded together at the two layers'perimeters such that the bond defines a fluid tight (e.g., airtight orwater tight) bladder.

FIG. 4B is a side view of the bending soft composite actuator 403 uponactuation when the bladder 411 is under fluid pressurization. Theanisotropic layer 401 performs a dual function of promoting lineargrowth of the elastic sections 407 while limiting its radial expansionto cause the assembly to bend.

In some embodiments, the strain limiting layer includes or is a secondcomposite layer comprising one or more second elastomeric sections andone or more second radially constraining sections, wherein the secondelastomeric section, the second radially constraining section, and thesecond composite layer have the same or different thickness, wherein thesecond composite layer is a monolithic anisotropic layer. Similar to thefirst composite layer, the second elastomeric section and the secondradially constraining section can be bonded together to form the secondcomposite layer. Alternatively, the second radially constraining sectionmay be encapsulated in the second elastomeric section. The radiallyconstraining sections may be evenly or unevenly distributed in thecomposite layer. In some embodiments, the radially constraining sectionscomprise radially constraining strips oriented parallel to one of theedges of the composite layer or at an angle to one of the edges of thecomposite layer. The angle (θ) can be in any ranges or have any values.In some embodiments, θ is about 10, 20, 30, 40, 45, 50, 60, 70, 80degree, or in any ranges bound by any two of the values disclosedherein. The soft composite actuator according to these embodiments isdescribed with reference to FIGS. 4C-4D.

FIG. 4C is a perspective view of an assembled linear extending softcomposite actuator 413 which consists of two anisotropic layers 415 and417 bonded together to form an airtight (or water tight) bladder. Thefirst composite layer 415 contains radially constraining sections 421made of strain limiting materials and elastomeric section 419 made ofelastic materials. Sections 419 and 421 are bonded together by thermal,chemical, and/or mechanical methods to form the monolithic firstcomposite layer. Sections 419 and 421 both have thickness the same asthat of the first composite layer 415.

The strain limiting layer 417 in FIG. 4C is also a second compositelayer containing radially constraining sections 425 made of strainlimiting materials and elastomeric section 423 made of elasticmaterials. Sections 423 and 425 are bonded together by thermal,chemical, and/or mechanical methods to form the monolithic firstcomposite layer. Sections 423 and 425 both have thickness the same asthat of the first composite layer 417.

Both layers 415 and 417 are anisotropic layers. FIG. 4D is a side viewof the linear extending actuator 413 before actuation (top portion ofFIG. 4D) and under fluid pressurization (lower portion of FIG. 4D) wherethe strain limiting sections (421 and 425) of the anisotropic layers 415and 417 form hoops that limit radial expansion and promote linearextension. As shown in FIG. 4D, upon actuation the actuator extends adistance of ΔL.

Thus, in these embodiments described above, the complexity of bondingmultiple material layers can be reduced by creating the desiredanisotropic properties into a single layer, e.g., the first or secondcomposite layer. The strain limiting sections (made of a strain limitedmaterial such as fibers, thread, non-woven materials, higher duromotermaterials, etc.) can be combined with the elastic sections to create asingle, monolithic layer that is more elastic in one direction (e.g.,y-direction in FIG. 4A) over another (e.g., x-direction in FIG. 4A).When this anisotropic layer is bonded to the strain limited layer theresult is a bending actuator constructed from only two material layers.The anisotropy contained in a single layer can be achieved several waysincluding molding or encapsulating the strain limited material in theelastic material, heat stamping the strain limited material togetherwith the elastomer, sandwiching two elastomer films around the strainlimited material, or cast extruding elastic and strain limitingmaterials together. Furthermore, adjusting the spacing and orientationof the elastic and strain limiting materials in the anisotropic layercan enable the soft actuator to combine multiple actuations in seriessuch as stiffening sections, bending sections, linear extendingsections, linear extending and twisting, and bend-twist sections (see,e.g., FIG. 5A for an example actuator with stiff sections and bendingsections). Similarly, the anisotropic layer can be bonded with anotheranisotropic layer to make a linear actuator (extending and contracting).

FIGS. 4A-F show that the direction of expansion can be controlled bycombining elastic material and strain limiting material into onemonolithic layer, which contains the elastomeric sections and theradially constraining sections. In some embodiments, the elastomericsections and the radially constraining sections are cast extrudingtogether, or embed fiber reinforcements could be used to create thestrain limiting property. The various applications and variationsdescribed with particularity for the multilayer versions of thecomposite layer actuator can also be achieved using the combinedelastomer/strain limiting material arrangement in a monolithic layer.

In some embodiments, the radially constraining section comprises aradial strain strip oriented parallel to one of the edges of the firstor second composite layer (see, e.g., FIGS. 4A and 4C).

In other embodiments, the radially constraining section comprises aradial strain strip oriented at an angle to one of the edges of thecomposite layer. For instance, FIG. 4E is an exploded and assembled viewof a soft composite actuator 427 capable of bending and twisting underfluid pressurization. As illustrated in FIG. 4E, a monolithic firstcomposite layer 433 is provided, containing radially constrainingsections 431 made of strain limiting materials and elastomeric sections429 made of elastic materials. Sections 431 and 429 are bonded togetherby thermal, chemical, and/or mechanical methods to form the monolithicfirst composite layer 433. Sections 429 and 431 both have thickness thesame as that of the first composite layer 433. As shown in FIG. 4E, theradially constraining section 431 is in the form of a radiallyconstraining strip, which is oriented in an angle (θ) with respect tothe layer 433's horizontal edge (shown as the y axis). θ can be in anyranges or have any values. In some embodiments, θ is about 10, 20, 30,40, 45, 50, 60, 70, 80 degree, or in any ranges bound by any two of thevalues disclosed herein. The angled elements, e.g., 431 or 429, in theanisotropic layer 433 can be evenly spaced, intermittently spaced,and/or at a gradient of angles. Angling the elastic and strain limitedelements in the anisotropic layer promotes linear growth at an angle tothe y-axis. As a result, when layer 433 is combined with a strainlimiting layer, e.g., 435, the resulting actuator 427 willsimultaneously bend and twist upon actuation.

FIG. 4F is an exploded and assembled view of an actuatable devicecapable of linear extension and twisting under fluid pressurization bybonding two anisotropic layers with angled elastic and strain limitingelements. A first composite layer 439, containing radially constrainingsections 445 (with an angle θ with respect to the layer 439's horizontaledge) and elastic sections 443, is combined with a second compositelayer 441, which contains similar elastic section 447 and radiallyconstraining section 449, to form a soft composite actuator 437. Whenactuated, soft composite actuator 437 extends linearly and twists.

In some embodiments, the soft composite actuator stiffens when actuatedand thus can be termed a stiffener. FIG. 5A shows the top view of anunactuated stiffener soft composite actuator 501 (top portion of FIG.5A) and the response of the actuator when actuated (bottom portion ofFIG. 5A) under fluid pressurization. The radially constraining layer 523of the actuator 501 contains cutout section 505 and solid sections 503.In this arrangement, the cut outs define areas where the actuator isallowed to bend and the solid sections, e.g., 503, of the radiallyconstraining layer restrict any actuation by inflating to form apressurized tube termed a stiffener.

FIG. 5B is an extension of FIG. 5A demonstrating that several bendingjoints 511 can be designed into a single actuator. In this illustration,the actuator 507 contains solid sections 509 (which stiffen uponactuation) and cutout sections 511 (which allow the actuator to bendduring actuation) in its radially constraining layer 519. As a result,this closed loop actuator 507 could be used to wrap around an object orto create an opening.

FIG. 5C is an extension of FIG. 5A demonstrating that multiple bendingactuators can be combined on a single laminate. In this figure, actuator513 contains four individual bending actuators which are arranged toform a grasping device. The actuator 513 has a radially constraininglayer 517 which contains openings, e.g., cutout sections 525 and solidsections 527. The bottom portion of FIG. 5C shows the scenario wherethree digits are activated when the bladder of the actuator is connectedto a pressurized fluid source via a tubing connection, while one is notconnected to the pressurized fluid source or is connected to a differentpressurized fluid source. In this figure, four individual bendingactuators are arranged to form a grasping device. As a result, the threedigits and the fourth digit can be controlled separately.

The locations of the openings, e.g., cutout sections and solid sectionscan be adjusted and arranged in any predetermined matter to achieve adesired actuation, e.g., any preferred ranges of motion or shapes of theactuated actuator. For example, as shown in FIG. 4E-4F, the radiallyconstraining sections can be arranged to be in an angle with respect tothe edge of the material layers of the actuator, which can producesimultaneous bending and twisting motion (not illustrated).

FIG. 6A depicts a top view and an isometric view of an actuatable device605 that combines a multiple functions onto a single laminate. In thisfigure, two bending actuators 601 (having cutouts in its radiallyconstraining layers) are connected via two stiffeners 603 (having solidsections in its radially constraining layers). The material layers ofthe actuator are bonded at perimeters such as 607. Thus, on a singlesheet, multiple functions can be achieved by using a single bladder. InFIG. 6A, the rectangular profile of the actuator 605 has a perimeterthermal bond and a second bond offset a certain distance inward (shownas 607). On two vertical sides (617) of the rectangle the radiallyconstraining layer has openings, e.g., cutouts that define a bendingactuator while on the other two sides, i.e., the horizontal sides 619,the radially constraining layer has no openings, e.g., cutouts, whichunder fluid pressurization becomes a stiff inflated tube that can beused to as a structural element.

FIG. 6B shows an actuator device 615 having multiple stiffeners used tosupport bending actuators and achieve greater coverage. In this figure,two bending actuators 611 (having cutouts in its radially constraininglayers) are connected via four stiffeners 613 (having solid sections inits radially constraining layers). The material layers of the actuatorare bonded at perimeters such as 609. In this embodiment, the actuatorcan be used to generate a bending motion with greater coverage. Forexample this could be used as a splint that can conform to the leg whilealso providing stability (i.e. stiffness) along the length of theinjury. In some embodiments, the single bladder of the actuator can beseparated into multiple bladders for more control over each function ofeach section of the actuator device. For example, the stiffeners mayneed to be separate bladders from the bending actuator because they mayoperate at different pressures.

In some embodiments, the soft composite actuator further comprises oneor more rigid elements attached to the strain limiting layer. Rigidelements could be added to actuator body to define discrete bendingpoints or to rigidize certain lengths for improved force transmission orstability. In some embodiments, rigid elements also enable a tighterbending radius of curvature and can be used as mounting substrate forauxiliary equipment.

FIG. 7A depicts an exploded view and cross-section view of an actuatabledevice 713 that incorporates rigid elements as an additional layer. Softactuator 713 contains a radially constraining layer 701, an elasticlayer 703, a strain limiting layer 705, and a rigid element layer 707containing rigid elements 709. These layers are stacked and bondedtogether to provide the actuator 713.

FIG. 7B is a side view of the bending actuator 713 under fluidpressurization with rigid elements where it only bends at the gapsbetween the rigid elements, e.g., position 715. FIG. 7B shows theactuator 713 with the four layers 701, 703, 705, and 707 described abovein FIG. 7A. Upon actuation, a portion of the elastic layer 711 mayexpand through the openings, e.g., cutouts in the radially constraininglayer 701. In some embodiments, the space between the rigid elements maybe increased to increase the radius of curvature.

The soft composite actuator as described herein may have a variety offunctions. In some embodiments, the soft composite actuator isconfigured to open an incision, move, displace organs, muscle, and/orbone, brace a joint, be worn to support joint movements, shape-match anobject, fold pre-defined bending joints to create origami-likestructures, achieve a sufficient grasp over the object, or create apadded layer conformal to the object.

In some embodiments, one of the material layers, e.g., the elasticlayer, is pre-strained before being bonded to the radially constraininglayer and/or the strain limiting layer. Pre-straining the elastic layercould be used to create a bimorph bending actuator. This could be usedas a way to make graspers that are low profile when unpressurized andcan conform around an object when pressurized. Any other type ofmaterial layer can be pre-strained as well.

FIG. 8A shows the assembly of a bimorph bending actuator thatincorporates a pre-strained layer during the assembly. The elastic layer803 is pre-strained along the directions of 807 and 809, before beingbonded to the radially constraining layer 801 and the strain limitinglayer 805. FIG. 8B shows the range of motion of the bimorph bendingactuator 825 at different stages of pressurization. Under no fluidpressurization (state 811), the pre-strained elastic layer causes theactuator 825 start in a curled position. Under partial fluidpressurization (state 813), the actuator 825 uncurls and straightensout. When the actuator is fully pressurized (state 815), it curls to theopposite side.

FIG. 8C illustrates that the opposing bimorph bending actuators can beused to form a grasper 827. At the unpressurized state 817, the graspercurls and does not grab object 823. At the partially actuated state 819,the grasper 827 only partially grabs object 823. Finally, when thegrasper 827 is fully pressurized (state 821), object 823 is tightlysurrounded by the grasper 827. Similarly a bimorph bending actuator canalso be created with two opposing bending actuators that are bondedtogether (or share the same strain limiting layer).

In some embodiments, the soft composite actuator is amulti-degree-freedom bending actuator. In some specific embodiments, thedegree of the actuation, e.g., bending of the soft composite actuatormay be controlled and fine-tuned by the fluid pressure inside thebladder. In some embodiments, the soft composite actuator is attached toone or more pneumatic or hydraulic connections. For instance, thepneumatic or hydraulic connections connected to the bladder, e.g., afluid pump, may apply different pressures to the fluid so result indifferent degrees of actuation, e.g., bending.

FIGS. 9A-9C are an extension of FIG. 4C where multiple linear extendingactuators can be grouped on the same laminate to form a multi-degree offreedom bending and extending actuator. In these figures, twoanisotropic layers (first composted layer 901 and second composite layer903 in FIG. 9B) are bonded together at locations shown as 911 such thatthey form three different bladders, 905, 907, and 909. Each of the firstand second composite layers has elastic sections 913 and radiallyconstraining sections 915. After bonding, three linear actuators, 917,919, and 921 are formed.

FIG. 9B is an end view of FIG. 9A (upper portion of FIG. 9B) and depictsthe next stage in the fabrication of a multi-degree of freedom bendingand extending actuator where the laminate is bonded end to end to form atube shape (lower portion of FIG. 9B) at end 923.

FIG. 9C illustrates that when one bladder of the actuator is selectivelypressurized it will linearly extend causing the tube structure to bendto an angle 0 (scenario 927). Fluid pressurization of one or morechambers/bladders causes bending and some linear extension. On the otherhand, equal pressurization of the all the bladders will cause theactuator to only extend linearly (scenario 929). Note that in scenario927, only one of the bladders is pressurized to have a pressure P₁,which is greater than the outside atmosphere pressure. In scenario 929,all of the three bladders are equally pressurized to have pressures P₁,P₂, and P₃, which are greater than the outside atmosphere pressure.

In some embodiments, the soft composite actuator as described herein maybe used for stabilizing a limb. In some embodiments, the soft compositeactuator is part of a splint or is the splint. In other embodiments, thesoft composite actuator is part of a grasper comprising a plurality ofdigits, or is grasper.

FIG. 10 is a perspective view of a wearable application where softactuators have been incorporated into a glove 1001 to assist jointmotions. The glove 1001 contains cutouts 1003 in its radiallyconstraining layer to accommodate the finger joint bending. The materiallayer-bonding approach enables the integration of a network of softactuators that can apply torques to finger joints to support handclosing. A similar configuration on the palm side could assist openingthe hand. With this approach, the material layers can serve a dualfunction of forming the actuators and serving as the glove material.

In some embodiments, one of material layers, e.g., the elastomericlayer, the strain limiting layer, the first and second composite layer(described below), and/or the radially constraining layer, is configuredto have one or more functions selected from the group consisting ofabsorbing fluids, transmitting light, changing color or luminescence,embedding a soft sensor, embedding a medical patch, embedding at least apart of an electronic circuit, embedding a heating element, and acombination thereof.

FIG. 11 is perspective view of a material layer described hereindemonstrating multi-functionality. In some embodiments, any of thematerial layers described herein can incorporate electronics, heatingelements, sensors, and so forth. As shown in FIG. 11 (left portion), aheating element 1105 may be incorporated into a material layer 1101,e.g., a strain limiting layer. Also shown in FIG. 11 (right portion), acircuit board or electronic element 1107 can be incorporated (e.g.,printed) into a material layer 1103, e.g., a strain limiting layer. Anyof the material layers described herein can have sensing capabilities byincorporating flex sensors, inertial measurement units (IMUs), or softsensors into the material layers.

FIG. 12 shows a sequence of side views of an actuatable device 1201 thatuses connected pressurized bladders to transmit force to lift an object.In step 1215, the actuator 1201 is formed by bonding multiple materiallayers at locations such as 1203. The actuator 1201 has three bladders,1205, 1207, and 1209, which are in fluidic communication with oneanother. In step 1217, a heavy object 1213 is placed on bladder 1207 andpressurized fluid 1211 is infused into the bladders. Bladders 1205 and1209 expand however bladder 1207 does not expand due to the gravityforce of object 1213. In step 1219, force F is applied onto bladders1205 and 1209. The force F can be applied by human or mechanical means.As a result, pressurized fluid is forced into bladder 1207 and causesbladder 1207 to expand and at the same time, move object 1213 upwardsfor a distance ΔD. Thus, the flexible nature of the material layersenables the bladder to operate in non-planar scenarios and the fluidtherein can be passed through a narrow opening, e.g., opening 1221.

In some embodiments, the soft composite actuator described herein can beprepared by bonding a portion of a pre-stacked laminate containing allthe material layers required for the soft composite actuator. Thematerial layers may be pre-stacked or rolled into a multi-layerlaminate. When in use, a desired size of the laminate may be removed,e.g., cut, and bonded to form the soft composite actuator. In someembodiments, two or more portions of the laminate can be cut and bondedtogether to form a soft actuating device including two or more softactuators descried herein.

In some embodiments, the pre-stacked laminate comprising a firstelastomeric laminate layer, a strain limiting laminate layer, and afirst radially constraining laminate layer. A portion of the laminate isseparated to provide the first elastomeric layer, the strain limitinglayer, and the first radially constraining layer stacked together. Theselayers may then be bonded together to provide a soft composite actuatordescribed herein.

In some embodiments, the pre-stacked laminate comprising a monolithic,first composite and a strain limiting laminate layer. A portion of thelaminate is separated to provide the first composite layer and thestrain limiting layer stacked together. These layers may then be bondedtogether to provide a soft composite actuator described herein.

FIG. 13A shows a sequence of images where a rolled sheet of actuatabledevices can be cut to a desired length and the bladders can be resealedwith a sealing tool. In step 1301, a plurality of material layers bondedat locations such as 1311 are rolled into a roll. During use, a desiredportion of the roll can be cut. The newly cut edge can be sealed using asealing tool 1313 (step 1303). The cut portion can be further divided asshown in step 1305, where the sealed edge 1319 remains sealed.

FIG. 13B illustrates how the cut portion of the material layer roll canbe assembled together to form a range of different actuatable devices.In step 1307, bending actuator 1321(which contains cutouts 1315 in itsradially constraining layer) and bending actuator 1325 (which containscutouts 1327 in its radially constraining layer) are joined together toa stiffening actuator 1323 (which contains solid strain limitingsections 1317 in its strain limiting layer). In step 1309, the resultingactuator device 1329 is actuated where the bending portions (1321 and1325) of the device bend, while the stiffening potion (1323) isstiffened. These illustrations present concepts where sheets of any softactuator described herein, e.g., bending, linear extending, contracting,bend/twist, and stiffening actuators, can be cut to length, sealed, andassembled into a range of configurations.

In certain embodiments, a packaging for holding the soft compositeactuator's material layer sheet can safely transmit the thermal bondingpattern without comprising the integrity of the package seal. In someembodiments, the soft composite actuator's material layers, e.g., theelastomeric layer, the strain limiting layer, the radially constraininglayer, the first composite monolithic layer, and/or the second compositemonolithic layer, are contained in a package. Bonding of portions of atleast two layers can be achieved by external means without thecompromise of the package to form the soft composite actuator withpredetermined shape. In some embodiments, the portions of at least twolayers are bonded by an external heat source that passes through thepackaging. In other embodiments, the package further comprises a heatingelement and bonding is achieved by heat generated from the activatedheating element. Non-limiting examples of heating element includeinduction heating, chemical reaction heating, or electrical heatingelements such as nichrome wire, graphite, and so forth.

FIG. 14 depicts a process by which the bladders of actuatable devicescan be defined while the layers of the laminate are contained withinpackaging (both sterile and non-sterile). The figure depicts packagingthat can safely transmit the thermal bonding pattern without reducingthe integrity of the package seal. This concept presents a solution tomeeting inventory needs. In step 1407, a sterile (or non-sterile)packaging 1403 holds the material layer sheet 1401 to be thermallybonded. The face of the packaging may contain a bonding pattern 1405. Instep 1409, a bonding device is used to thermally (or chemically ormechanically) bond the desired bladder along the thermal bonding pattern1413 labelled on the face of the packing Thus, in step 1409, thermalbond pattern (a rectangle in this case) has been transferred to thecontents of the package while still maintaining the sterility of thepackage contents. When the soft composite actuator 1415 is needed, it isremoved from the packaging (step 1411).

In yet another aspect, a method of actuation is described, including:

-   -   providing a soft composite actuator of any of the embodiments        described herein; and    -   pressurizing the bladder with a fluid, wherein the soft        composite actuator actuates in a predetermined manner.

In some embodiments, the material layers are arranged and bonded tocreate structural anisotropy. In some embodiments, actuation of the softcomposite actuator achieves one or more motions selected from the groupconsisting of bending motion, combination bending, twisting motion,linear extension, a combination of linear extension and twist, linearcontraction, a combination of linear contraction and twist, and anycombination thereof. In some specific embodiments, the soft compositeactuator stiffens upon fluid pressurization. The bladder may be inflatedto different pressures to achieve a tunable stiffness surface. Thedifferent pressures may be controlled or tuned by the externalpressurized fluid source.

In yet another aspect, a soft actuating device is described, including aplurality of the soft composite actuators described in any of theembodiments herein. The plurality of the soft composite actuators may beconnected to the same fluid source, or to two or more different fluidsource. In certain embodiments, the soft actuating device includes afirst and a second soft composite actuators described in any of theembodiments herein. The first soft actuator may be connected to a firstpressurized fluid source and the second soft actuator may be connectedto a second pressurized fluid source. Thus, the first and the secondsoft composite actuators may be actuated separately or alternately, byalternately actuating the first and second fluid sources. In somespecific embodiments, the first soft actuator is a stiffener describedherein. In some specific embodiments, the second soft actuator is abending actuator described herein. Thus, the soft actuating device maybe controlled to enable different motions, e.g., bending or stiffening,by actuating different fluid sources connected to the bladders of theindividual soft composite actuators in the soft actuating device.

In yet another aspect, a method of making a soft composite actuatoraccording to any of the embodiments described herein is disclosed,including:

-   -   providing a first elastomeric layer, a strain limiting layer,        and a first radially constraining layer; wherein the elastomeric        layer is disposed between the radially constraining layer and        the strain limiting layer; and    -   bonding the first elastomeric layer, the strain limiting layer,        and the first radially constraining layer to form sealed        parameters defining at least one bladder for holding pressurized        fluid.

In some embodiments, providing a first elastomeric layer, a strainlimiting layer, and a first radially constraining layer comprisesproviding a pre-stacked laminate comprising a first elastomeric laminatelayer, a strain limiting laminate layer, and a first radiallyconstraining laminate layer; and separating part of the laminate toprovide the first elastomeric layer, the strain limiting layer, and thefirst radially constraining layer stacked together. Thus, the materiallayers of the soft composite actuator may be pre-stacked and cut andbond when needed.

In yet another aspect, a method of making a soft composite actuatoraccording to any of the embodiments described herein is disclosed,including:

-   -   providing the first composite layer described herein and the        strain limiting layer; and    -   bonding portions of the first composite layer and the strain        limiting layer to form sealed parameters defining at least one        bladder for holding pressurized fluid. In some embodiments, the        strain limiting layer includes a second composite layer        described herein.

In some embodiments, providing the first composite layer and the strainlimiting layer comprises: providing a pre-stacked laminate comprising afirst composite laminate layer and a strain limiting laminate layer; andseparating part of the laminate to provide the first composite layer andthe strain limiting layer stacked together.

The bonding may be achieved by a method selected from the groupconsisting of thermal method, chemical method, mechanical method, and acombination thereof. In some embodiments, the method further includesremoving excess material from the soft composite actuator after bonding.

In yet another aspect, a method of using the soft actuator of any one ofthe embodiments for one or more functions is described, wherein thefunction is selected from the group consisting of distribute forces,mixing material, handling material, lifting, grasping, steering aphotovoltaic cell or a mirror, steering material on a surface.

In some embodiments, steering material on a surface comprises movingliquid around or moving a solid object.

While for purposes of illustration, embodiments of this invention havebeen shown and described, other forms thereof will become apparent tothose skilled in the art upon reference to this disclosure and,therefore, it should be understood that any such departures from thespecific embodiment shown and described are intended to fall within thespirit and scope of this invention.

We claim:
 1. A soft composite actuator, comprising: a strain limitinglayer; a first radially constraining layer; and a first elastomericlayer disposed between the first radially constraining layer and thestrain limiting layer; wherein the first elastomeric layer, the strainlimiting layer, and the first radially constraining layer are bondedtogether to form at least one bladder for holding pressurized fluid. 2.The soft composite actuator of claim 1, the bond is selected from thegroup of thermal bonds, chemical bonds, mechanical bonds andcombinations thereof.
 3. The soft composite actuator of claim 1, whereinthe soft composite actuator further comprises a second elastomeric layerdisposed adjacent to the first elastomeric layer and the strain limitinglayer comprises a second radially constraining layer.
 4. The softcomposite actuator of claim 1, wherein the radially constraining layercomprises one or more radially constraining sections.
 5. The softcomposite actuator of claim 4, wherein the radially constrainingsections comprise radially constraining strips evenly or unevenlydistributed in the radially constraining layer.
 6. The soft compositeactuator of claim 5, wherein the radially constraining strips areoriented parallel to one of the edges of the radially constraining layeror at an angle to one of the edges of the radially constraining layer.7. The soft composite actuator of claim 5, wherein the radiallyconstraining strips are bonded to the first elastomeric layer.
 8. Thesoft composite actuator of claim 1, wherein the radially constraininglayer comprises one or more strain limiting sections free from anyopenings.
 9. The soft composite actuator of claim 1, wherein theradially constraining layer comprises: one or more openings throughwhich one or more portions of the adjacent first elastomeric layerexpand upon actuation, and one or more strain limiting sections freefrom any openings.
 10. The soft composite actuator of claim 1, whereinthe first elastomeric layer, the strain limiting layer, and the firstradially constraining layer are bonded together to form a plurality ofbladders for holding pressurized fluid.
 11. The soft composite actuatorof claim 1, wherein the soft composite actuator further comprises one ormore rigid elements attached to the strain limiting layer.
 12. The softcomposite actuator of claim 1, wherein the bladder is designed toaccommodate a pressurized fluid selected from the group consisting of agas and a liquid.
 13. The soft composite actuator of claim 1, whereinone of the elastomeric layer, the strain limiting layer, and theradially constraining layer is configured to absorb fluids, transmitlight, change color or luminescence, embed a soft sensor or a medicalpatch, embed at least a part of an electronic circuit or a heatingelement, and a combination thereof.
 14. The soft composite actuator ofclaim 1, wherein the soft composite actuator is part of a splint, agrasper, or a glove comprising a plurality of digits, or is a splint, agrasper, or a glove.
 15. A soft composite actuator, comprising: amonolithic, first composite layer comprising one or more firstelastomeric sections and one or more first radially constrainingsections; and a strain limiting layer, wherein the first composite layerand the strain limiting layer are bonded together to form at least onebladder for holding pressurized fluid.
 16. The soft composite actuatorof claim 15, wherein the strain limiting layer comprises a monolithic,second composite layer comprising one or more second elastomericsections and one or more second radially constraining sections.
 17. Thesoft composite actuator of claim 15, wherein the first and/or secondelastomeric section, the first and/or second radially constrainingsection, and the first and/or second composite layer have the samethickness.
 18. The soft composite actuator of claim 15, wherein thefirst and/or second elastomeric section and the first and/or secondradially constraining section have different thickness.
 19. The softcomposite actuator of claim 18, wherein the first and/or second radiallyconstraining section is encapsulated in the first and/or secondelastomeric section.
 20. The soft composite actuator of claim 15,wherein the first and/or second elastomeric sections and the firstand/or second radially constraining sections are bonded together. 21.The soft composite actuator of claim 15, the bond is selected from thegroup of thermal bonds, chemical bonds, mechanical bonds andcombinations thereof.
 22. The soft composite actuator of claim 15,wherein the radially constraining sections comprise radiallyconstraining strips oriented parallel to one of the edges of thecomposite layer or at an angle to one of the edges of the compositelayer.
 23. The soft composite actuator of claim 22, wherein the radiallyconstraining strips are evenly or unevenly distributed in the compositelayer.
 24. The soft composite actuator of claim 15, wherein the firstcomposite layer and the strain limiting layer are bonded together toform a plurality of bladders for holding pressurized fluid.
 25. The softcomposite actuator of claim 15, wherein the soft composite actuatorfurther comprises one or more rigid elements attached to the strainlimiting layer.
 26. The soft composite actuator of claim 15, wherein thebladder is designed to accommodate a pressurized fluid selected from thegroup consisting of a gas and a liquid.
 27. The soft composite actuatorof claim 15, wherein one of the layers is configured to absorb fluids,transmit light, change color or luminescence, embed a soft sensor or amedical patch, embed at least a part of an electronic circuit or aheating element, and a combination thereof.
 28. The soft compositeactuator of claim 15, wherein the soft composite actuator is part of asplint, a grasper, or a glove comprising a plurality of digits, or is asplint, a grasper, or a glove.
 29. A soft actuating device comprising aplurality of the soft composite actuators of claim
 1. 30. The softactuating device of claim 29 comprising: a first soft composite actuatorconnected to a first fluid source; and a second soft composite actuatorconnected to a second fluid source.
 31. A soft actuating devicecomprising a plurality of the soft composite actuator of claim
 15. 32. Amethod of actuation comprising: providing a soft composite actuator ofclaim 1 or 15; and pressurizing the bladder with a fluid, wherein thesoft composite actuator actuates in a predetermined manner.
 33. Themethod of claim 32, wherein actuation of the soft composite actuatorachieves one or more motions selected from the group consisting ofbending motion, combination bending, twisting motion, linear extension,a combination of linear extension and twist, linear contraction, acombination of linear contraction and twist, and any combinationthereof.
 34. The method of claim 32, wherein the soft composite actuatoris configured to open an incision or move, displace organs, muscle,and/or bone, brace a joint, be worn to support joint movements,shape-match an object, fold pre-defined bending joints to createorigami-like structures, achieve a sufficient grasp over the object,create a padded layer conformal to the object, distribute forces, mixmaterial, hand material, lift object, grasp object, steer a photovoltaiccell or a mirror, or steer material on a surface.
 35. The method ofclaim 32, wherein the pressurized fluid is temperature-regulated. 36.The method of claim 32, wherein the soft composite actuator stiffensupon fluid pressurization.
 37. The method of claim 32, wherein thebladder is configured to be inflated to a first degree of stiffnessunder a first fluid pressure or to a second degree of stiffness under asecond fluid pressure different from the first fluid pressure.
 38. Amethod of actuation comprising: providing the soft actuating device ofclaim 29; and pressurizing one or more bladders with one or more fluids,wherein the soft actuating device actuates in a predetermined manner.39. A method of actuation comprising: providing the soft actuatingdevice of claim 30; and pressurizing the first soft composite actuator'sbladder and the second soft composite actuator's bladder alternately byactivating the first fluid source and the second fluid sourcealternately.
 40. The method of claim 39, wherein the first softcomposite actuator bends upon actuation and the second soft compositeactuator stiffens upon actuation.
 41. A method of making a softcomposite actuator of claim 1, comprising: providing a first elastomericlayer, a strain limiting layer, and a first radially constraining layer;wherein the elastomeric layer is disposed between the radiallyconstraining layer and the strain limiting layer; and bonding the firstelastomeric layer, the strain limiting layer, and the first radiallyconstraining layer to form sealed parameters defining at least onebladder for holding pressurized fluid.
 42. The method of claim 41,wherein providing a first elastomeric layer, a strain limiting layer,and a first radially constraining layer comprises: providing apre-stacked laminate comprising a first elastomeric laminate layer, astrain limiting laminate layer, and a first radially constraininglaminate layer; and separating part of the laminate to provide the firstelastomeric layer, the strain limiting layer, and the first radiallyconstraining layer stacked together.
 43. A method of making a softcomposite actuator of claim 15, comprising: providing the firstcomposite layer and the strain limiting layer; and bonding the firstcomposite layer and the strain limiting layer to form sealed parametersdefining at least one bladder for holding pressurized fluid.
 44. Themethod of claim 43, wherein providing the first composite layer and thestrain limiting layer comprises: providing a pre-stacked laminatecomprising a first composite laminate layer and a strain limitinglaminate layer; and separating part of the laminate to provide the firstcomposite layer and the strain limiting layer stacked together.
 45. Themethod of claim 41 or 43, wherein the bond is selected from the group ofthermal bonds, chemical bonds, mechanical bonds and combinationsthereof.
 46. The method of claim 41 or 43, wherein the elastomericlayer, the strain limiting layer, and the radially constraining layerare contained in a package.
 47. The method of claim 46, wherein bondingis achieved by external heat passing through the packaging or internalheat generated by a heating element inside the packaging without thecompromise of the package.
 48. The method of claim 41 or 43, wherein theelastomeric layer or the first composite layer is in a pre-strainedstate before bonding.
 49. The method of claim 41 or 43, wherein one ofthe layers has a non-planar shape before or during bonding.